earthing SWA gland

[sharpe]

Hi, i would like to make sure i understand this properly.


On a TNS supply, using 3 core SWA to run a sub-main, and using the third core for CPC, where the SWA gland terminates into a plastic enclosure, how is it best to earth the armour?


Am i right that you run a fly lead (the same size CSA as the live conductors) from the banjo/piranha nut, back to the MET?


Or do you run a bonding conductor from the banjo/piranha nut, to the earth terminal inside the enclosure the gland is terminating into?


Or can you do either


Thanks

 

[Simonslimline]

The SWA needs earthing regardless of earthing system. If you are not using the armour as a CPC then i would just earth it at the supply end with a flying lead, either a banjo or piranha nut as you have mentioned.

If using the armour as CPC then it would need earthing at both ends.

What size CSA is this SWA?

 

[Octopus]

I would mount a metal adaptable box directly below the CU. The swa would be gland into that and then an earth lead would run into the CU from there. Obviously the 3 cores run directly into the CU

 

[Richard Burns]

You are confusing earthing with bonding from your description.
The armour of SWA needs to be earthed and not bonded.
Earthing is ensuring a solid path to earth for fault current to allow the PD to operate in the case of a fault.
For SWA a fly lead from the gland needs to be connected to the adjacent earth terminal (generally where the SWA cores are terminated).

 

[sharpe]

The SWA is 6mm, it doesn't actually terminate at the main CU.

The sub-main comes from DP henley blocks, in 16mm tails to a 40a switch fuse, then 6mm T&E and 6mm earth single to a whiska box where it connects to the SWA, the SWA gland then is terminated using a whiska earth bar, the SWA then runs to new consumer unit.

My question is do i run a 6mm fly lead from the whisk earth bar, right the way back to the MET at the main `CU? (which is what i thought was required)

Or as i think you guys are suggesting, connect the fly lead from the whisk earth bar to the earth terminal inside the whiska box to the same terminal as the CPC? (where the SWA cores are terminated)

 

[Simonslimline]

As has been stated, you are earthing the SWA as it is part of the electrical system and is not an extraneous conductive part. Don't get this confused with Main protective bonding.

 

[Richard Burns]

Connect the fly lead from the wiska earth bar to the earth terminal inside the wiska box to the same terminal at which the SWA core CPC is terminated